Question 415:

Asked on September 27, 2008

Tags: Interquartile Range

1

Answer:

No answer provided yet.

Sort your data from lowest to highest. Count up all your values. If you have for example 20 values, the 25th percentile is equal to the 5th values (20*.25 = 5). The 75th percentile is the 15th value (20*.75 = 15).  It doesn't always work as nicely if you have certain odd numbers. For example, at a sample of 14, the 25th percentile is (14*.25 = 3.5).  If possible, pick a value between 3 and 4.

Once you have the 25th & 75th you just subtract the 75th-25th percentile and get the middle 50 percent of values.